Los Angeles, June 21 (AHN) Mayor Karen Bass of the US city of Los Angeles on Sunday declared a local emergency in response to an ongoing warehouse fire that erupted Wednesday and generated heavy smoke, which has spread across the Los Angeles metropolitan area for several days.

"I'm issuing an emergency declaration to ensure the city has the resources it needs as this operation continues and to keep the community safe," Bass said in a statement. "We're in contact with the governor because this has escalated to a problem where we are very concerned about the health of the community."

The emergency declaration is intended to unlock additional state resources for a complex operation that city officials described as larger than a routine structure fire. The fire broke out Wednesday afternoon at a Lineage Logistics cold-storage facility, where officials said tens of millions of pounds of frozen food are stored in a massive refrigerated building near downtown Los Angeles, Xinhua news agency reported.

Fire officials said the building, roughly 46,000 square meters, presents unusual hazards because of its construction and contents. Los Angeles Fire Department Chief Jaime Moore described the facility as "like a giant cooler," with corrugated steel walls packed with dense foam insulation and reinforced interior panels.

Once ignited, officials said, that insulation can smolder slowly, trap heat and produce persistent smoke even as crews pour water onto the structure from outside.

The fire also involved solar panels on the roof and a refrigeration system that used ammonia, prompting an early hazardous-materials response. Officials said crews mitigated that chemical threat by shutting down valves and removing ammonia and other refrigerants from the site. But the longer the fire burns, they said, the more attention is shifting to the enormous quantity of frozen food inside the facility and the possibility that decaying products could create a new environmental and public health problem.

Moore said the food stored in the building includes frozen bread and meat products.

"I wouldn't say it's potentially dangerous; it would be unpleasant," he told NBC Los Angeles. "It would be a horrible odor, but what we're looking at is what those gases would produce or create. We've already mitigated the hazardous materials portion by removing the ammonia and other chemicals that were used as refrigerants ... now, it's really what's going to happen when this food starts decomposing?"

The blaze has been difficult to attack directly. Firefighters initially worked to stop flames spreading across the roof, but officials said interior conditions -- including poor visibility, unstable debris and the continued burning of hidden materials -- have made entry unsafe. Crews have relied on exterior firefighting, aerial ladder pipes and repeated helicopter water drops, an unusual tactic for a commercial structure fire, to cool the building and prevent the flames from extending to nearby homes or other parts of the industrial complex.

The Los Angeles Fire Department said Saturday that the smell of smoke had reached much of the city and urged residents to limit exposure as much as possible, but no evacuation orders were active Saturday. Still, authorities warned that smoke can irritate the lungs and pose added risks for children, older adults and people with respiratory or heart conditions.

As of Saturday afternoon, officials reported no injuries to firefighters or civilians.

Lineage Logistics, the tenant and operator of the building, said in a statement reported by the Los Angeles Times that it believed the fire began while third-party contractors were testing the solar array on the roof. The cause remains under investigation.